Soft actuator using thermoelectric effect

ABSTRACT

The present invention relates to a soft actuator moving linearly against external stimuli whose expansion and contraction can be actively controlled, suggesting that the actuator of the invention overcomes the problems of the conventional soft actuators, The soft actuator of the present invention can be repetitively driven quickly and accurately by controlling heating and cooling by using thermoelectric effect and, the soft actuator of the present invention can realize bending, tensioning, compression, and rotational driving of a tubular device containing a driver.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a soft actuator.

2. Description of the Related Art

An actuator indicates a driving device that drives a machine usingpower. The actuator may refer to an electric motor or any hydraulic orpneumatically actuated piston or cylinder device having any type ofcontrol mechanism in the mechatronics field. In recent years, a softactuator or a micro actuator, which can be applied to artificialmuscles, has been recently developed using a new material.

A soft actuator is a flexible apparatus that can deliver the enteredpower or displacement through a flexible body, unlike the conventionalmechanism that delivers the entered power or displacement through theconventional rigid body.

The soft actuator is largely divided as follows: a bistable actuatorusing a jump phenomenon to move from an unstable point to a stable pointby arranging the potential wells at two locations; a conductive polymeractuator using an electroactive polymer; and a string reinforcedactuator using a string twist like the target technology.

The string reinforced actuator is classified according to the directionof string movement.

In general, a soft actuator that is driven by an external stimulusincluding a string reinforced actuator uses electricity, temperature,and light applied at one end as an external stimulus source.

In particular, there is a method to give a temperature stimulus to asoft actuator by using Joule heat. Joule heat can be explained as aphenomenon in which heat is generated when current flows through ahighly resistant wire. The reason why Joule heat is generated is thatfree electrons in the wire actively move and cause many collisions withatoms, and the kinetic energy of the atoms is converted into heat energydue to the collision. At this time the heat generated by the resistanceis called Joule heat. In other words, Joule heat is the heat convertedfrom electric energy. In electrical wiring or transmission lines in thegeneral machinery, Joule heat causes a huge energy loss therein. So, itis important to draw a plan that can minimize the generation of Jouleheat. Also, Joule's law is established with regard to the consumption ofelectric energy that can produce Joule heat.

When a soft actuator is driven by using Joule heat, fast temperaturechange can be induced during the actuator is heated by the generation ofJoule heat, but the temperature change is going to be very slow duringthe cooling, which draws a limitation in the driving of the actuator.

In relation to the prior arts involved in a soft actuator, Korean PatentPublication No 10-2016-0091656 (referred ‘prior art’ hereinafter)describes ‘Torsional actuators by temperature gradient and energyharvesting device using the same’. The prior art takes the heat energypossibly with temperature gradient that can be obtained from an outerenvironment as a power source to operate the soft actuator. That is,there is a difficulty in inducing the operation of the additionalconfiguration due to the driver because it does not adopt an additionalconfiguration for driving the driver.

Therefore, the present inventors developed a soft actuator that containsan additional configuration to supply energy in order to control theactuator and can overcome the disadvantages of the conventional actuatorusing Joule heat by using thermoelectric heat instead.

In the meantime, an actuator can be used to drive a catheter. Thecatheter is one of the common names of tubular instruments, and can bemade of different materials in different sizes and shapes according tothe purpose of use. The use of the catheter is to discharge the fluid inthe body cavity or various organs, aspirate the perfusion fluid forcleaning, measure the cardiovascular behavior or central venouspressure, and inject the drug or contrast agent into the body

An actuator can also be used to drive an endoscope. The endoscopy is adevice designed to observe such an organ that is hard to observe itslesions without surgery or autopsy by inserting a machine therein.Commonly used endoscope types include bronchoscope, esophagoscope,gastroscope, duodenoscope, rectoscope, cystoscopy, and laparoscope.Other special cases include thoracoscopy, mediastinoscope, andcardioscope. The endoscope can be in the form of a direct scope that isthe shape of one tube through which an organ can be observed with thenaked eye, or uses a lens system, or is equipped with a camera, or canbe in the form of a string scope using a glass string. A gastrocameracan be used to detect and diagnose fine stomach lesions by inserting asmall camera in the stomach and directly photographing and recording thestomach mucosa. In the meantime, a gastrostringscope has an excellentresolving power and can be equipped with an apparatus capable of cuttingthe lesional tissue directly while observing for further examination.

The tube type actuator can be realized in various ways. A bimetal methodis the most representative example. The bimetal method is a method usinga metal with two kinds of thin metal plates which are different indegree of expansion by heat. The metal is mainly formed by depositing ametal layer on a SiO₂ layer (insulating layer) on which a current pathmade of polysilicon is buried. Since the thermal expansion coefficientof the SiO₂ layer (insulating layer) is different from that of the metallayer, when voltage is applied to the thermal micro-actuator, adisplacement is generated in the side having a small coefficient ofthermal expansion and is driven in such a manner as to bend.

Another type of the actuator is the differential resistance type. Thedifferential resistance type actuator is made of polysilicon, the singlematerial. The differential resistance type actuator is composed of ahigh temperature part and a low temperature part having electrodes towhich voltage is applied. The high temperature part has a smallcross-sectional area, the low temperature part has a largecross-sectional area, and is configured so that the opposite ends of theside having the electrode are connected to each other. When voltage isgiven to the electrode of the low temperature part and the hightemperature part not connected to the differential resistance typeactuator, current flows through the pathway comprising the hightemperature part and the low temperature part. By the difference of thearea between the high temperature part and the low temperature part, thedifference in resistance is caused and accordingly the different levelof Joule heat is generated. As a result, the temperature becomesdifferent between the high temperature part and the low temperaturepart. In the differential resistance type actuator, the difference inthermal expansion is caused by the difference of the temperature and asa result, displacement moves to cause bending from the high temperaturepart to the low temperature part.

In relation to the prior arts involved in the actuator, Korean Patent No10-0789268 (referred ‘prior art’ hereinafter) describes “Thermalexpansion micro actuator, micro mirror formed directly on the same,micro mirror actuating apparatus using thermal expansion micro actuator,and lightswitch using the same”. However, this prior art has a problemthat the driving direction is limited to the driving in which thedriving direction is biased in both directions with respect to thesingle axis as the driving device that is driven in accordance with theexpansion ratio of the high temperature part and the low temperaturepart.

PRIOR ART REFERENCE Patent Reference

Korean Patent Publication of unexamined applications No. 10-2015-0038475

Korean Patent Publication No. 10-2016-0091656

Korean Patent No. 10-0789268

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a soft actuator thatcan reduce the operation response time of the soft actuator byconverting the natural cooling dependent operation into the forcedcooling dependent operation.

It is another object of the present invention to overcome the problemsof the conventional soft actuator in order to provide a new actuatorwhose expansion and contraction can be actively controlled and movementis forced linearly according to external stimuli.

It is also an object of the present invention to provide a soft actuatorthat can drive repetitively, fast and accurately, by controlling heatingand cooling using thermoelectric effect.

It is further an object of the present invention to provide a softactuator for the realization of bending, tensioning, compression, androtation of a tubular device including a driver.

The soft actuator according to an example of the present inventionincludes a string that is contracted or expanded by heating or cooling;and a thermoelectric element that can heat or cool the string asarranged at least one side of the string.

The string may further have twist or twist and coiling feature.

The thermoelectric element can be arranged at least on a portion of thesurface of the string.

At this time, a control unit to control the direction of current flowingthrough the thermoelectric element can be additionally included.

Also, an adhesive layer connecting the surface of the string and thethermoelectric element can be additionally included.

The thermoelectric element can be expanded or contracted by theexpansion and contraction of the string.

The method for preparing the soft actuator according to an example ofthe present invention comprises the steps of preparing a string that istwisted; and arranging a thermoelectric element at least on a portion ofthe surface of the string.

The method above can additionally include a step of coiling the stringbefore the step of arranging the thermoelectric element at least on aportion of the surface of the string.

The method above can additionally include a step of coiling the stringafter the step of arranging the thermoelectric element at least on aportion of the surface of the string.

The soft actuator according to an example of the present inventionincludes the first string and the second string having twist; and thethermoelectric element arranged in between the first string and thesecond string.

The first string above is showing forward reaction by the thermoelectricelement and the second string above is showing reverse reaction by thethermoelectric element.

The first and the second strings and the thermoelectric element abovecan be coiled.

The first and the second strings and the thermoelectric element abovecan be arranged horizontally.

The first and the second strings and the thermoelectric element abovecan be arranged vertically.

The thermoelectric element above can heat or cool down the side of thestring.

The thermoelectric element can control the movement of the string byregulating the temperature of the string surface by heating or cooling.

The thermoelectric element above can also be flexible.

The soft actuator according to an example of the present inventioncontains the thermoelectric element arranged on one side of the stringand can be expanded or contracted according to the change of thedirection of current flowing through the thermoelectric element.

At this time, the thermoelectric element can be laminated in multiplelayers.

Also, an adhesive layer connecting the surface of the string and thethermoelectric element can be additionally included.

A control unit can also be additionally included to connect thethermoelectric element to one side of the string.

The soft actuator according to an example of the present inventioncomprises a driving part composed of the first string that can becontracted or expanded by heating or cooling and the second string thatmoves against the first string by heating or cooling wherein the stringsare arranged not to be contacted with each other while both making oneunit; and a thermoelectric element part that heats or cools the drivingpart, in which a conductor region is arranged against the driving partin order to heat or cool the first string and the second string.

Preferably, the soft actuator can additionally include a power supplypart that can form a closed circuit together with the thermoelectricelement part and can supply current to the thermoelectric element part.

Preferably, the soft actuator of the invention can additionally includea string part composed of flexible strings that is arranged in parallelto the side of the unit above.

Preferably, the thermoelectric element part is crossed over the top sideor the bottom side of the first string and the second string and thefirst string and the second string are arranged facing opposite eachother from the thermoelectric element part as a center.

Preferably, the driving part may cool any one of the first string andthe second string with the heat energy transferred from thethermoelectric element part and heat the other string so that the unitbody can realize a single drive.

Preferably, the driving part has multiple units arranged in parallel.

Preferably, the thermoelectric element part comprises the firstconductive body, the second conductive body that generates another heatflow to the different direction from the one induced by the firstconductive body, and the conductor arranged in between the firstconductive body and the second conductive body in parallel.

Preferably, the thermoelectric element part can heat or cool down theconductor since it has two separated conduction pathways through whichcurrent flows through the first conductive body, passes through theconductor and then arrives at the second conductive body; and currentflows through the second conductive body, passes through the conductorand then arrives at the first conductive body.

Preferably, the driving part accomplishes a single drive since the firststring and the second string is contracted or expanded by heating orcooling the conductor.

Preferably, in the driving part, a driving surface is formed byarranging a plurality of the unit bodies in parallel; and the drivingsurface forms a cylindrical side wall together with the string partcomposed of flexible strings that is connected to the side of the unitabove in parallel, side by side. The thermoelectric element part has aconduction pathway on one side of the driving surface through whichcurrent flows through the first conductive body, passes through theconductor and arrives at the second conductive body; and the otherconduction pathway on the other side of the driving surface throughwhich current flows through the second conductive body, passes throughthe conductor and arrives at the first conductive body. This pair of thedriving surface realizes different movements of contraction or expansionwhen current is provided from the thermoelectric element part, and as aresult it can create bending moment.

The soft actuator according to an example of the present inventioncharacteristically comprises a driving part composed of the first stringhaving twist and coiling and can be contracted or expanded by heating orcooling and the second string having twist and coiling and can becontracted or expanded by heating or cooling and is arranged withmaintaining distance from the first string; and a driving cable having ahollow in which the unit body is intruded.

Preferably, in the driving part, one of the strings, the first stringand the second string, is the homochiral string wherein twist andcoiling are made in the same direction and the other is the heterochiralstring wherein twist and coiling are made in different direction.

Preferably, the driving part includes an electric heating body togenerate heat by using the applied current and the electric heating bodyherein can deliver heat energy to the first string and the secondstring.

Preferably, in the driving part, the first string and the second stringwhich forms the unit can be driven differently by contraction orexpansion when they are heated or cooled down.

Preferably, the driving part may include a plurality of unit bodies, andthe driving cable may include a plurality of hollows corresponding tothe number of the unit bodies.

Preferably, in the driving part, the driving of the plurality of unitbodies is controlled independently to enable tension, compression,bending, and rotation of the driving cable.

Advantageous Effect

The soft actuator according to an example of the present invention andthe method for preparing the same can reduce the operation response timeof the soft actuator by converting the natural cooling dependentoperation into the forced cooling dependent operation.

Also, it is possible to solve the problems of the conventional softactuator, to control expansion and contraction actively, and to operatelinearly against external stimuli.

The soft actuator of the invention is also advantageous in improvingaccuracy and in broadening the field of application by manipulating thestring accurately by using the twisted string and the thermoelectricelement.

The soft actuator of the invention can be applied to medical robots andmicro artificial muscles that utilize microactuators due to its simplestructure using the twisted string and the thermoelectric element, andalso applicable to military robots and body function-complementaryrobots due to its excellent hardness and strong moving force.

The actuator of the invention is also advantageous in eliminating otherexternal factors and in accurate controlling by the thermoelectricelement since it does not use light or chemicals but use athermoelectric element that is close to the string.

The actuator of the present invention also can increase the heating andcooling efficiency of the thermoelectric element by disposing thestrings on both sides of the thermoelectric element and can reduce thewaste heat of the thermoelectric element.

The soft actuator including the driving part and the thermoelectricelement part of the present invention can generate bending moment inboth directions by repeating heating and cooling quickly and accurately,so that it can be applied as a band driver to the elbow or kneeincluding the joint, suggesting that the actuator of the invention isadvantageous in commercialization as a muscle supplementary band tosupport the muscular strength of aged people and patients who are inweakness of muscular strength.

According to the present invention, the soft actuator can realize notonly bending but also tension, compression, and rotation by the drivingpart including the unit body composed of the homochiral string and theheterochiral string and by using the driving cable in which the drivingpart is intruded.

The soft actuator of the present invention can be applied to variousfields such as a blood vessel moving robot, a driver of a soft robot,and a gripper for gripping an object by being applied without limitingthe size.

BRIEF DESCRIPTION OF THE DRAWINGS

The application of the preferred embodiments of the present invention isbest understood with reference to the accompanying drawings, wherein:

FIG. 1 illustrates the string having twist.

FIG. 2 illustrates the string having twist and coiling.

FIG. 3 illustrates the behavior of the heterostring.

FIG. 4 illustrates the behavior of the homostring.

FIG. 5 illustrates the soft actuator according to an example of thepresent invention.

FIG. 6 illustrates the cross-section of FIG. 5 A.

FIG. 7 illustrates the behavior of the soft actuator according to anexample of the present invention.

FIG. 8 illustrates the soft actuator according to another example of thepresent invention.

FIG. 9 illustrates the soft actuator according to another example of thepresent invention.

FIG. 10 illustrates the soft actuator according to another example ofthe present invention.

FIG. 11 illustrates the soft actuator according to another example ofthe present invention.

FIG. 12 illustrates the soft actuator according to another example ofthe present invention.

FIG. 13 illustrates the cross-section of FIG. 12 B.

FIG. 14 illustrates the cross-section of a region of the soft actuatoraccording to another example of the present invention where thethermoelectric element is disposed.

FIG. 15 illustrates the soft actuator according to another example ofthe present invention.

FIG. 16 illustrates the soft actuator according to another example ofthe present invention.

FIG. 17 illustrates the soft actuator according to another example ofthe present invention.

FIG. 18 illustrates the soft actuator according to an example of thepresent invention.

FIG. 19 is the perspective view of FIG. 18.

FIG. 20 illustrates the soft actuator according to another example ofthe present invention.

FIG. 21 illustrates the soft actuator according to another example ofthe present invention.

FIG. 22 illustrates the soft actuator according to another example ofthe present invention.

FIG. 23 illustrates the soft actuator according to another example ofthe present invention.

FIG. 24 illustrates the soft actuator according to an example of thepresent invention.

FIG. 25 illustrates the unit body according to an example of the presentinvention.

FIG. 26 illustrates the driving part or the driving surface according toan example of the present invention.

FIG. 27 illustrates the thermoelectric element part according to anexample of the present invention.

FIG. 28 illustrates the soft actuator including the string partaccording to an example of the present invention.

FIG. 29 illustrates the cylindrical band of the soft actuator accordingto an example of the present invention.

FIG. 30 illustrates the spreaded cylindrical band of the soft actuatoraccording to an example of the present invention.

FIG. 31 is the perspective view of the soft actuator according to anexample of the present invention.

FIG. 32 illustrates the unit body constructing a driving part of thesoft actuator according to an example of the present invention.

FIG. 33 is a cross-sectional view of the soft actuator according to anexample of the present invention.

FIG. 34 illustrates the compression or tension of the soft actuatoraccording to an example of the present invention.

FIG. 35 illustrates the bending of the soft actuator according to anexample of the present invention.

FIG. 36 illustrates the rotation of the soft actuator according to anexample of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention is described in detail.

Soft Actuator (100)

The present invention provides a soft actuator comprising a string thatis contracted or expanded by heating or cooling; and a thermoelectricelement that can heat or cool the string as arranged at least one sideof the string.

The soft actuator (100) according to an example of the present inventionmay contain a thermoelectric element (120) arranged at least one side ofthe string surfaces.

FIG. 5 illustrates the soft actuator (100) according to an example ofthe present invention, and FIG. 6 illustrates the cross-section of FIG.5 A.

As shown in FIGS. 5 and 6, the soft actuator (100) according to anexample of the present invention comprises the twisted string (110); andthe thermoelectric element (120) arranged at least one side of thestring; wherein the string (110) is contracted or expanded according tothe change of the direction of current flowing through thethermoelectric element (120).

Previously, the actuator was designed to move the string (lengthdecrease/increase) by heating and then to recover the string back to theoriginal length (length increase/decrease) by natural cooling.Accordingly, there might be non-symmetrical response time of movement byheat and the recovery from the movement by cooling. However, the softactuator (100) of an example of the present invention comprises thethermoelectric element (120) for the behavior, so that the operationtime of the soft actuator can be reduced by heating and cooling thestring (110) by modifying the heating surface and the cooling surface tothe direction of current flow.

The soft actuator (100) according to an example of the present inventioncomprises the string (110) either twisted or twisted and coiled, so thatit can respond sensitively and quickly to the temperature changereversibly.

When the temperature of the string (110) is raised by the thermoelectricelement (120) arranged in the soft actuator (100), the soft actuator(100) is getting torque as the coiled or twisted string structurebecomes loosened. When the raised temperature of the string (110) goesdown by the thermoelectric element (120) arranged in the soft actuator(100), the coiled or twisted string structure is recovered, resulting inthe reverse torque. By this mechanism, the soft actuator (100) can beheated and cooled down actively. Instead of consuming heat energypassively by the soft actuator (100), the heat energy is converted intomechanical energy to cool down the rotary type soft actuator (100).

In the conventional art, the soft actuator is working to move the stringby heating (length reduction/increase) and then to recover the stringback to the original length (length increase/reduction) by naturalcooling. At this time, asymmetry occurs in the behavior time when thesoft actuator is heated to move the string and cooled to recover thestring back to the original position.

According to an example of the present invention, the soft actuator(100) comprises the thermoelectric element (120) on at least one side ofthe twisted string (110) for the behavior, so that the string (110) canbe heated or cooled down by changing the heating surface and the coolingsurface according to the direction change of current flowing through thethermoelectric element (120). That is, the natural cooling system isconverted into the forced cooling system, so that the operation responsetime of the soft actuator (100) can be reduced. For heating/cooling thesoft actuator (100), the thermoelectric element (120) is arranged as amoving source. Therefore, the contraction/expansion of the string (110)is achieved by heating/cooling the thermoelectric element (120). As aresult, the continuous operation characteristics of the soft actuator(100) using heat can be improved.

Hereinafter, by referring FIGS. 1˜4, the string having the twistedstructure included in the soft actuator (100) of the present inventionis described.

FIG. 1 illustrates the string having twist. In FIG. 1, the string istwisted in a certain direction with showing bended grain.

In an example of the present invention, the string (110) can be selectedfrom the group consisting of such polymers as nylon, shape memorypolyurethane, polyethylene, and rubber, but not always limited thereto.If the string is one of those polymers, the soft actuator (100) canmaintain the reversible structure wherein the string is untwisted andretwisted even at a high temperature and thereby durability and lifetimewould be extended, suggesting that the actuator can be applied invarious fields. The string (110) herein provides the reversible rotationmovement, meaning once it is transformed by the high temperature or thelow temperature, it can be recovered back to the initial twisted form.

The method to make the string (110) being twisted is either to fix oneside and to rotate the other or to rotate both sides. The string (110)may have the structure wherein multiple strands are twisted each other.At this time, the string (110) having the twisted structure made byrotating both sides independently to the opposite directioncharacteristically ends up the structure of chiral Z type or chiral Stype.

FIG. 2 illustrates the string (110) having twist and coiling. As shownin FIG. 2, the string may have twist and coiling. The string (110) canhave stronger driving force by heating and cooling and can response moreaccurately and sensitively by having twist and coiling. The method ofimparting coiling to the string is not particularly limited.

For example, one side of the string is fixed and the other side of thestring is rotated to be coiled, or the string is wound up with a pipe tomake the coiling structure.

FIG. 3 illustrates the behavior of the heterostring, and FIG. 4illustrates the behavior of the homostring.

The string (110) can be twisted to the right or to the left (twist) andthen wound up to the right or to the left (coiling). When the stringtwisted to the left is wound up to the left or when the string twistedto the right is wound up to the right, it is called ‘homochiral string’.When the string twisted to the left is wound up to the right or when thestring twisted to the right is wound up to the left, it is called‘heterochiral string’.

The homochiral string increases in length when heated by thethermoelectric element (120) and decreases in length when cooled down bythe thermoelectric element (120). The heterochiral string shows theopposite action. So, it decreases in length when heated by thethermoelectric element (120) and increases in length when cooled down bythe thermoelectric element (120).

So, the direction of movement caused by the thermoelectric element (120)can be regulated by controlling the direction of twist and coiling ofthe string (110).

The thermoelectric element (120) can be arranged at least on one side ofthe twisted string (110). The thermoelectric element (120) can bearranged on the string necessary for the control of the movement of thesoft actuator (100). As shown in FIG. 5, the thermoelectric element(120) may be formed to surround a part of the surface of the string(110) in a cylindrical shape, or may be formed so as to surround theentire side of the string (110).

The thermoelectric element (120) is one of the energy conversion devicesfor converting electric energy into heat energy. The thermoelectricelement (120) makes the soft actuator (100) take action actively byheating or cooling the surface of the string by changing the directionof flowing current.

The thermoelectric element includes a thermoelectric power generatingdevice using Seebeck effect which is the effect of generatingelectromotive force by the temperature difference and a cooling deviceusing Peltier effect which is the effect of generating or absorbing heatwhen current is flowing in but the present invention is not limitedthereto.

The thermoelectric element (120) may be formed of a bulk structure inwhich a thermoelectric material made of N-type and P-type semiconductorsis formed on a ceramic substrate such as alumina (Al₂O₃), and the N-typethermoelectric material (123) and the P-type thermoelectric material(122) are connected in series to an electrode.

The thermoelectric element (120) comprises the first electrode (121),the N-type thermoelectric material (123) and P-type thermoelectricmaterial (122) formed on the first electrode (121), and the secondelectrode (124) for the serial connection of the first electrode (121)and the N-type thermoelectric material (123) and the P-typethermoelectric material (122) together.

The actuator can also be composed of the first substrate, the firstelectrode (121) arranged on the first substrate, the N-typethermoelectric material (123) and the P-type thermoelectric material(122) arranged on the first electrode (121), the second electrode (124)arranged on the N-type thermoelectric material (123) and the P-typethermoelectric material (122), and the second substrate layered on thesecond electrode (124). At this time, the soft actuator (100) accordingto an example of the present invention can be prepared by arranging thecompleted thermoelectric element on the surface of the string.

The thermoelectric element (120) can be prepared by forming the firstelectrode (121) in a regular pattern on the surface of the twistedstring (110) and by forming the N-type thermoelectric material (123) andthe P-type thermoelectric material (122) on the top of the firstelectrode stepwise and lastly by forming the second electrode (124) onthe of the same. The second electrode (124) can be formed by contactingthe top of the substrate on which the second electrode (124) is formedin a regular pattern. The N-type thermoelectric material (123) and theP-type thermoelectric material (122) can be connected in series by thefirst electrode (121) and the second electrode (124).

The N-type thermoelectric material (123) and the P-type thermoelectricmaterial (122) are alternately arranged in the first electrode (121) soas to be easily connected in series by the electrodes. The said P-typethermoelectric material (122) can comprise at least one of thosecompounds, Si, Al, Ca, Na, Ge, Fe, Pb, Sb, Te, Bi, Co, Ce, Sn, Ni, Cu,Na, K, Pt, Ru, Rh, Au, W, Pd, Ti, Ta, Mo, Hf, La, Ir, and Ag. Forexample, the N-type thermoelectric material (123) can be BixTe1-x andthe P-type thermoelectric material (122) can be SbxTe1-x.

The N-type thermoelectric material (123) and the P-type thermoelectricmaterial (122) can be formed in the form of a thick film having thethickness of a few˜hundreds of micrometer (μm).

The first electrode (121) and the second electrode (124) can be formedto electrically connect the N-type thermoelectric material (123) and theP-type thermoelectric material (122) in series. The first electrode(121) and the second electrode (124) can be arranged such that the firstelectrode (121) is disposed on the surface of the string, all theelectrodes can be formed on the thermoelectric material, or all theelectrodes can be formed on the bottom of the thermoelectric material.

The first electrode (121) and the second electrode (124) are preferablythose metals which have excellent electrical conductivity, which areexemplified by nickel (Ni), aluminum (Al), copper (Cu), platinum (Pt),ruthenium (Ru) (Au), tungsten (W), cobalt (Co), palladium (Pd), titanium(Ti), tantalum (Ta), iron (Fe), molybdenum (Mo), hafnium (Hf), lanthanumIridium (Ir), and silver (Ag).

The thermoelectric element (120) is arranged on the surface of thestring (110) and can be expanded or contracted with the string (110).Also the thermoelectric element has to be able to operate in response tovolume expansion, contraction, or bending of the string (110). Thus, thethermoelectric element (120) may have flexibility.

For the flexibility, the first electrode (121), the N-typethermoelectric material (123), and the P-type thermoelectric material(122), and the second electrode (124) can be composed of those materialsthat have flexibility or include the composition having flexibility.

Particularly, the first electrode (121), the N-type thermoelectricmaterial (123), the P-type thermoelectric material (122), and the secondelectrode (124) of the thermoelectric element (120) can include aconductive polymer. The first electrode (121) and the second electrode(124) are formed in the form of nanowires, so that electrical shortingmay not occur even when the thermoelectric element is expanded andcontracted corresponding to the expansion or contraction of the strings.In addition, the first electrode (121), the N-type thermoelectricmaterial (123), the P-type thermoelectric material, and the secondelectrode (124) of the thermoelectric element (120) may have a shapeincluding pores therein to cope with the expansion or contraction of thestring.

The N-type thermoelectric material (123) can include a bismuth-tellurium(BixTe1-x) compound, and the P-type thermoelectric material (122) caninclude an antimony-tellurium (SbxTe1-x) compound.

At this time, the conductive polymer included in the first electrode(121), the N-type thermoelectric material (123), the P-typethermoelectric material (122), and the second electrode (124) can beorganic conducting polymers such asPoly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS),Poly(fluorene)s, Polyphenylenes, Polypyrenes, Polyazulenes,Polynaphthalenes, Poly(acetylene)s (PAC), Poly(p-phenylene vinylene)(PPV), Poly(pyrrole)s (PPY), Polycarbazoles, Polyindoles, Polyazepines,Polyanilines (PANI), Poly(thiophene)s (PT),Poly(3,4-ethylenedioxythiophene) (PEDOT), and Poly(p-phenylene sulfide)(PPS) and might include organic non-conducting polymers such asPolydimethylsiloxane (PDMS), Poly(methylmethacrylate), Poly(p-phenyleneterephthalamide), and Polyethylene.

The substrate included in the thermoelectric element (120) can be aflexible substrate so that the thermoelectric element (120) can haveflexibility. The flexible substrate is to support the wholethermoelectric element and at the same time to give flexibility to thethermoelectric element, which is exemplified by a polyimide film, aKapton film, a polyester film, a PEN film, a plastic film, PDMS, andpaper, but not always limited thereto. It is preferable that theflexible substrate is made of a material having heat resistance enoughto withstand the subsequent process temperature.

The first electrode (121), the N-type thermoelectric material (123), theP-type thermoelectric material (122), and the second electrode (124) ofthe thermoelectric element (120) can include a conductive polymer. Theconductive polymer can includepoly-3,4-ethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS),polyaniline, polyacetylene or polyphenylene vinylene, but not alwayslimited thereto.

The first electrode (121) and the second electrode (124) are formed inthe form of nanowires, so that electrical shorting may not occur evenwhen the thermoelectric element is expanded and contracted correspondingto the expansion or contraction of the string. In addition, the firstelectrode (121), the N-type thermoelectric material (123), the P-typethermoelectric material, and the second electrode (124) of thethermoelectric element (120) may have a shape including pores therein tocope with the expansion or contraction of the string.

The N-type thermoelectric material (123) and the P-type thermoelectricmaterial (122) are alternately arranged on the first electrode (121) andconnected in series by the first electrode (121).

Herein, the N-type thermoelectric material (123) and the P-typethermoelectric material (122) include pores therein, and at least someof those pores are filled with organic polymer materials.

FIG. 7 illustrates the behavior of the soft actuator (100) according toan example of the present invention. As shown in FIG. 7, the softactuator (100) of the present invention can be expanded and contractedby supplying current to the thermoelectric element (120) arranged on thesurface of the string (110). So, the operation response time of the softactuator (100) can be reduced by converting the natural coolingdependent operation into the forced cooling dependent operation.

FIG. 8 illustrates the soft actuator (200) according to another exampleof the present invention.

As shown in FIG. 8, the soft actuator (200) of the invention canadditionally include the control unit (230) to control the direction ofcurrent flowing through the thermoelectric element (220).

The control unit (230) can change the direction of current flowingthrough the thermoelectric element (220), by which the temperature ofthe surface of the string can be raised or lowered (heating or cooling)to make the soft actuator (200) operate actively.

FIG. 9 illustrates the soft actuator (300) according to another exampleof the present invention.

As shown in FIG. 9, the soft actuator includes the adhesive layer (340)to connect the string (310) and the thermoelectric element (320). Theadhesive layer (340) can be disposed between the thermoelectric element(320) and the string (310), which plays a role of adhering the firstelectrode of the thermoelectric element (320) onto the surface of thestring (310). When the substrate is included in the thermoelectricelement (320), the substrate can be contacted with the surface of thestring (310). The adhesive layer (340) can include metal epoxy, forexample silver (Ag) epoxy. The adhesive layer (340) may be an adhesive,yet have a high electrical conductivity, and may have a suitableviscosity to allow deformation when appropriate pressure is applied.

The adhesive layer (340) can include a binder, which is exemplified by athermoplastic resin. The thermoplastic resin herein can be selected fromthe group consisting of acrylonitrile resin, phenoxy resin, butadieneresin, acrylic resin, urethane resin, polyamide resin, olefin resin,string-reinforced resin, and NBR (nitrile butadiene rubber) resin, butnot always limited thereto. The binder used for the adhesive layer (340)can be the binder resin not comprising an epoxy group. The thermoplasticresin preferably has a weight average molecular weight of1,000˜1,000,000 g/mol. Within the above range, it is possible to haveproper film strength, to prevent phase separation, and to adhere to theconductive layer or the non-conductive layer, so that the adhesivestrength is not lowered. The preferable concentration of the binder inthe adhesive layer (340) is 20˜70 weight % by the weight of the solidcomponent. The concentration in that range favors the film formation.

The adhesive layer (340) can additionally include hydrophobic stringrica and/or other additives, if necessary. In that case, the preferableamount of the additionally included additive is 1˜10 weight % by theweight of the solid component.

FIG. 10 illustrates the soft actuator (400) according to another exampleof the present invention.

As described hereinbefore, the string included in the soft actuator(400) according to an example of the present invention has the structureof twist and coiling. At this time, the thermoelectric element (420)arranged on the string (410) can be formed before the coiling process.As shown in FIG. 10, the thermoelectric element (420) can be formed towrap the side of the string (410). Before the coiling process of thestring (410), deposition process or adhesion process can be performed toform the thermoelectric element (420). At this time, the string (410)and the thermoelectric element (420) of the soft actuator (400) cancontact with each other on a large surface, so that the soft actuator(400) can be operated more accurately and faster, and higher power canbe obtained.

FIG. 11 illustrates the soft actuator (500) according to another exampleof the present invention.

According to FIG. 11, when the thermoelectric element (520) is formed onthe coiled string (510), the thermoelectric element might not bearranged in the inside of the coiling area or in the region where thestrings contact with each other during the deposition process oradhesion process. Through this process, it is possible to preventbreakage of the thermoelectric element that may occur due to the processof imparting coiling to the string.

FIG. 12 illustrates the soft actuator (600) according to another exampleof the present invention and FIG. 13 illustrates the cross-section ofFIG. 12 B.

As shown in FIGS. 12 and 13, the soft actuator (600) according to anexample of the present invention includes the twisted string (610) andthe thermoelectric element (620) arranged on at least one side of thestring (610).

The actuator can be operated by heating or cooling the surface of thestring (610) by converting the direction of current flowing through thethermoelectric element (620) arranged on both ends of the string. Bythat system, the symmetrical response to the contraction/expansion ofthe soft actuator (600) can be configured to improve the operatingcharacteristics and increase the usability of the soft actuator (600).

Conventionally, heat is applied to move the string (lengthreduction/increase) and return to its original position (lengthincrease/reduction) by natural cooling. At this time, there might beasymmetrical difference between the time for driving by heat and thetime driving by cooling. In an example of the present invention, thethermoelectric element for driving is arranged in the soft actuator andthe heating surface and the cooling surface of the thermoelectricelement can be converted by changing the direction of current flowingtherein, suggesting that the operating response time of the softactuator can be reduced by heating or cooling the string.

When the temperature of the string (610) of the soft actuator (600) israised by the thermoelectric element (620) arranged on one side of thestring, the twisted or coiled structure of the soft actuator (600)becomes loose, by which the actuator gains the rotational force. Whenthe temperature of the string (610) of the soft actuator (600) islowered by the thermoelectric element (620), the loosened structure isrecovered back to the original coiled or twisted structure, during whichthe rotational force in the opposite direction is generated.

The string (610) herein can be selected from the group consisting ofsuch polymers as nylon, shape memory polyurethane, polyethylene, andrubber, but not always limited thereto. When a polymer is used as thestring, the soft actuator (100) can maintain its reversible structurebetween untwist and retwist for a long time even at a high temperatureand also maintain durability and longer life time, so that it can beapplied to various fields. The string (610) provides a reversiblerotational movement back to the initial twisted form even if the shapeis deformed by high or low temperature.

The string (610) can be the string described in the example explainedhereinbefore.

The thermoelectric element (620) can be the one described in another theexample described hereinbefore, but not always limited thereto.

FIG. 14 illustrates the cross-section of a region of the soft actuator(600) according to another example of the present invention where thethermoelectric element (620) is disposed. As shown in FIG. 14, themultiple thermoelectric elements (620) can be arranged in the layeredstructure in order to apply sufficient heat to the string (610). At thistime, the first electrode (721 a) is disposed on the cross-section ofthe string (610), and the N-type thermoelectric material (723 a) and theP-type thermoelectric material (722 a) are disposed on the firstelectrode (721 a). Then, the second electrode (724 a) is arranged on theN-type thermoelectric material (723 a) and the P-type thermoelectricmaterial (722 a). After placing the first thermoelectric element in thisway, the second thermoelectric element can be placed across theinsulating layer (750). The first electrode (721 b) can be arranged onthe insulating layer (750) and the N-type thermoelectric material (723b) and the P-type thermoelectric material (722 b) can be arranged on thefirst electrode (721 b) and then the second electrode (724 b) can beplaced on the N-type thermoelectric material (723 b) and the P-typethermoelectric material (722 b). The first thermoelectric element andthe second thermoelectric element may be connected in series by wires.By arranging the same heating surface and cooling face toward thecross-section of the string, the movement of the soft actuator (600) canbe more accurately controlled and the power can be strengthened.

FIG. 15 illustrates the soft actuator (600) according to another exampleof the present invention.

The thermoelectric element allows the actuation of the soft actuator(600) by heating or cooling the surface of the string by changing thecurrent direction. The control unit (830) can be connected to thethermoelectric element by a wire, by which the movement thereof can becontrolled.

FIG. 16 illustrates the soft actuator (600) according to another exampleof the present invention. As shown in FIG. 16, in the soft actuator(600) according to another example of the present invention, the stringand the thermoelectric element are connected with each other by theadhesive layer (940) arranged in between the cross-section of the string(610) and the thermoelectric element (620). The adhesive layer (940) caninclude metal epoxy, for example silver (Ag) epoxy. The adhesive layer(940) may be an adhesive, yet have a high electrical conductivity, andmay have a suitable viscosity to allow deformation when appropriatepressure is applied.

FIG. 17 illustrates the soft actuator (1000) according to anotherexample of the present invention.

As shown in FIG. 17, the string (1010) may have twist and coiling. Thestring (1010) can have stronger driving force by heating and cooling andcan response more accurately and sensitively by having twist andcoiling. The method of imparting coiling to the string is notparticularly limited. For example, one side of the string is fixed andprocessed while the other side of the string is rotating, resulting inthe coiling structure. Or, the coiling structure can be produced bywrapping a pipe with the string.

The soft actuator (100) according to an example of the present inventioncan include the first string and the second string and thethermoelectric element can be arranged between the first string and thesecond string.

FIG. 18 illustrates the soft actuator (100) according to an example ofthe present invention and FIG. 19 is the perspective view of FIG. 18.

As shown in FIGS. 18 and 19, the soft actuator (100) according to anexample of the present invention comprises the twisted first string(111) and the second string (121), and the thermoelectric element (120)arranged between the first string (111) and the second string (131).

Conventionally, heat is applied to move the string (lengthreduction/increase) and return to its original position (lengthincrease/reduction) by natural cooling. At this time, there might beasymmetrical difference between the time for driving by heat and thetime driving by cooling.

In an example of the present invention, the thermoelectric element (120)for driving is arranged in the soft actuator (100) and the heatingsurface and the cooling surface of the thermoelectric element (120) canbe converted by changing the direction of current flowing therein,suggesting that the operating response time of the soft actuator (100)can be reduced by heating or cooling the first string (111) and thesecond string (131).

The soft actuator (100) according to an example of the present inventioncomprises the first string (111) and the second string (131) eithertwisted or twisted and coiled, so that it can respond sensitively andquickly to the temperature change reversibly.

The thermoelectric element (120) above can increase the heating orcooling efficiency by contacting physically with the first string (111)and the second string (131). In addition, the thermoelectric element isphysically spaced apart from the first string and the second string toprevent the physical force from being transmitted to the thermoelectricelement as the first string and the second string are expanded orrelaxed.

When the temperature of the first string (111) and the second string(131) is raised by the thermoelectric element (120) arranged in the softactuator (100), the soft actuator (100) is getting torque as the coiledor twisted structure of the first string (111) and the second string(131) becomes loosened. When the raised temperature of the first string(111) and the second string (131) goes down by the thermoelectricelement (120) arranged in the soft actuator (100), the coiled or twistedstructure is recovered, resulting in the reverse torque. By thismechanism, the soft actuator (100) can be heated and cooled downactively. Instead of consuming heat energy passively by the softactuator (100), the heat energy is converted into mechanical energy tocool down the rotary type soft actuator (100).

FIG. 20 illustrates the soft actuator (200) according to another exampleof the present invention. As shown in FIG. 20, the soft actuator (200)of the invention can additionally include the control unit (230) tocontrol the direction of current flowing through the thermoelectricelement (220).

The control unit (230) can change the direction of current flowingthrough the thermoelectric element (220), by which the temperature ofthe surface of the first string (211) and the second string (231) can beraised or lowered (heating or cooling) to make the soft actuator (200)operate actively.

FIG. 21 illustrates the soft actuator (300) according to another exampleof the present invention. As shown in FIG. 21, in the soft actuator(300) of the present invention, the thermoelectric element (320) may bedisposed between the first string (311) and the second string (331) in athree-dimensional shape corresponding to the first string (311) and thesecond string (331). Although the thermoelectric element (320) has anarrow area as compared with the plate type, the area contributing toheating or cooling the first string (311) and the second string (331)can be sufficiently large. Therefore, the production cost can be reducedby disposing the thermoelectric element (320) in a zigzag shape as shownin FIG. 21, or arranging the thermoelectric element (320) in parallelwith the side way of the first string (311) or the second string (331).When the first string (311) or the second string (331) is expanded orcontracted, the thermoelectric element (320) can respond more easily tothe movement of the first string (311) or the second string (331).

The thermoelectric element (320) can contact physically with the firststring (311) or the second string (331). The thermoelectric element canbe arranged between the first string and the second string withmaintaining distance from them. The thermoelectric element (320) can bethe same as explained in another example hereinbefore, but not alwayslimited thereto.

FIG. 22 illustrates the soft actuator (400) according to another exampleof the present invention. As explained hereinbefore, the first string(411) and the second string (431) included in the soft actuator (400)according to an example of the present invention can have the structureof twist and coiling.

At this time, the thermoelectric element (420) arranged in between thefirst string (411) and the second string (431) can be formed before thecoiling process. That is, after the thermoelectric element (420) isarranged between the first string (411) and the second string (431),coiling can be imparted to the bundle of the first string (411), thethermoelectric element (420), and the second string.

Alternatively, the soft actuator can be prepared in which the firststring (411), the second string (431), and the thermoelectric element(420) are coiled and then the first string (411), the second string(431), and the thermoelectric element (420) are assembled.

The thermoelectric element (420) disposed between the first string (411)and the second string (431) can be placed horizontally to the maindriving axle of the soft actuator (400). The main behavior of the softactuator (400) is longitudinal motion of the actuator, whether elongatedor contracted in the longitudinal direction.

As shown in FIG. 22, the first string (411), the thermoelectric element(420), and the second string (431) are arranged vertically to thedirection of coiling. So, the first string (411) is heated or cooledaccording to the heating or cooling of one side of the thermoelectricelement (420), and the second string (431) is cooled or heated accordingto the cooling or heating of the other side of the thermoelectricelement (420). That is, the first string (411) and the second string(431) can perform the positive and reverse reactions simultaneously,suggesting that the soft actuator (400) can increase the efficiency inpower and operating time.

The first electrode and the second electrode of the thermoelectricelement (420) are directly or indirectly connected to the first string(411) and the second string (431), and the P-type thermoelectricmaterial and the N-type thermoelectric material are arranged by turns inbetween the first electrode and the second electrode. The thermoelectricelement (420) can be connected to the first string (411) and the secondstring (431) by the adhesive layer. The thermoelectric element (420)above can be the same as the one described in another example of theinvention, but not always limited thereto.

FIG. 23 illustrates the soft actuator (500) according to another exampleof the present invention. As explained hereinbefore, the first string(511) and the second string (531) included in the soft actuator (500)according to an example of the present invention can have the structureof twist and coiling.

At this time, the thermoelectric element (520) arranged in between thefirst string (511) and the second string (531) can be formed before thecoiling process. That is, after the thermoelectric element (520) isarranged between the first string (511) and the second string (531),coiling can be imparted to the bundle of the first string (511), thethermoelectric element (520), and the second string (531).

Alternatively, the soft actuator can be prepared in which the firststring (511), the second string (531), and the thermoelectric element(520) are coiled and then the first string (511), the second string(531), and the thermoelectric element (520) are assembled.

The thermoelectric element (520) disposed between the first string (511)and the second string (531) can be placed horizontally to the maindriving axle of the soft actuator (500). The main behavior of the softactuator (500) is longitudinal motion of the actuator, whether elongatedor contracted in the longitudinal direction.

As shown in FIG. 23, the first string (511), the thermoelectric element(520), and the second string (531) are arranged horizontally to thedirection of coiling. So, the first string (511) is heated or cooledaccording to the heating or cooling of one side of the thermoelectricelement (520), and the second string (531) is cooled or heated accordingto the cooling or heating of the other side of the thermoelectricelement (520). That is, the first string (511) and the second string(531) can perform the positive and reverse reactions simultaneously,suggesting that the soft actuator (500) can increase the efficiency inpower and operating time.

The first electrode and the second electrode of the thermoelectricelement (520) are directly or indirectly connected to the first string(511) and the second string (531), and the P-type thermoelectricmaterial and the N-type thermoelectric material are arranged by turns inbetween the first electrode and the second electrode. The thermoelectricelement (520) can be connected to the first string (511) and the secondstring (531) by the adhesive layer. The thermoelectric element (520)above can be the same as the one described in another example of theinvention, but not always limited thereto.

Further, the present invention provides a soft actuator comprising:

a driving part as one unit comprising the first string that can beexpanded or contracted by heating or cooling, the second string that canmove oppositely to the first string by heating or cooling, wherein thefirst string and the second string are not contacted with each other;and

a thermoelectric element part to heat or cool the driving part.

At this time, the thermoelectric element part is arranged with thedriving part so that the area where the conductor is formed can heat orcool the first string and the second string.

(Patent 5)

FIG. 24 illustrates the soft actuator (1) according to an example of thepresent invention.

The soft actuator (1) according to an example of the present inventioncan include a driving part (11), a thermoelectric element part (13), apower supply part (15), and a string part (17, FIG. 29).

The soft actuator (1) comprises a driving part (11) composed of thefirst string (1101) that can be contracted or expanded by heating orcooling and the second string (1103) that moves against the first stringby heating or cooling wherein the strings are arranged not to becontacted with each other while both making one unit; and athermoelectric element part (13) that heats or cools the driving part(11), in which a conductor region (133) is arranged against the drivingpart (11) in order to heat or cool the first string (1101) and thesecond string (1103).

As shown in FIG. 24, the soft actuator (1) according to an example ofthe present invention might not include the string part (17, FIG. 28).The soft actuator (1) can have the first string (1101) and the secondstring (1103) arranged by turns. The first string (1101) or the secondstring (1103) of the soft actuator (1) can be either homochiral orheterochiral fiber or both. The first string (1101) and the secondstring (1103) can be different strings in different structures. In thesoft actuator (1), the first string (1101) and the second string (1103)can construct one unit (1100). In the soft actuator (1), the unit (1100)can be connected in parallel. The thermoelectric element part (13) canbe arranged by crossing over the unit (1100) connected in parallel inthe soft actuator (1).

The soft actuator (1) can additionally include the power supply part(15) to form a closed circuit with the thermoelectric element part (13)and to provide current to the thermoelectric element part (13).

In an example of the present invention, the soft actuator (1) can beconnected in series with the power supply part (15) and thethermoelectric element part (13). The soft actuator (1) can generateheat energy by flowing current through the thermoelectric element part(13) connected in series to the power supply part (15). The softactuator (1) can transmit the heat energy generated in thethermoelectric element part (13) to the driving part (11). The drivingpart (11) provided the heat energy generates bending moment in the softactuator (1), by which the soft actuator (1) can drive.

The soft actuator (1) can additionally include the string part (17, FIG.28) composed of flexible strings connected in parallel to the side ofthe unit (1100).

As shown in FIG. 28, the soft actuator (1) according to an example ofthe invention can additionally include the string part (17) to supportthe movement of the driving part (11). The soft actuator (1) shown inFIG. 28 is described in more detail in the following example 1.

The soft actuator (1) can have the structure wherein the thermoelectricelement part (13) is crossing over the top side or the bottom side ofthe first string (1101) and the second string (1103) and the firststring (1101) and the second string (1103) are arranged in the oppositeside.

In an example of the present invention, in the soft actuator (1), thedriving part (11) and the thermoelectric element part (13) can bearranged in various forms. For example, the driving part (11) isarranged on top side of the thermoelectric element part (13) in the softactuator (1). Or the driving part (11) can be arranged on the bottomside of the thermoelectric element part (13) in the soft actuator (1).In particular, the driving part (11) and the thermoelectric element part(13) can cross over each other in the soft actuator (1). At this time,the driving part (11) and the thermoelectric element part (13) can beconnected tightly with each other due to the structural characteristicsof the soft actuator (1).

FIG. 1 illustrates the twisted structure of the string constructing thedriving part (11) of the soft actuator (1) according to an example ofthe present invention.

The string that can compose the driving part (11) of the soft actuator(1) according to an example of the present invention can be the firststring (1101) or the second string (1103). The string composing thedriving part (11) of the soft actuator (1) can be homostring orheterostring. The string constituting the driving part (11) of the softactuator (1) can be selected from the group consisting of such polymersas nylon, shape memory polyurethane, polyethylene, and rubber. By usingsuch polymers as the string forming the soft actuator (1), the softactuator (1) can maintain the reversible structure wherein the string isuntwisted and retwisted even at a high temperature. The string formingthe soft actuator (1) can be changed not only by heating but also bycooling, so that it can provide a reversible rotation movement to goingback to the initial coiled structure.

As shown in FIG. 1, the string forming the driving part (11) of the softactuator (1) according to an example of the present invention isprimarily twisted. To give the twisted structure to the string formingthe driving part (11) of the soft actuator (1), one end of the string isfixed and the other end of the string is rotated or both ends arerotated.

FIG. 2 illustrates the coiling structure of the string constructing thedriving part (11) of the soft actuator (1) according to an example ofthe present invention.

As shown in FIG. 2, the string forming the driving part (11) of the softactuator (1) can be twisted first and then the twisted string can becoiled additionally. A method to make the string forming the drivingpart (11) of the soft actuator (1) coiled is not limited to a specificone. As an example, one side of the string is fixed and the other sideof the string is rotated to make the coiling structure. Or, the stringwraps a pipe to make the string coiled. When the string is twisted andcoiled at the same time, the driving force of the string induced byheating and cooling becomes strong and the characteristics of the stringcan be changed according to the direction of the twist and coiling.

FIG. 4 illustrates the homochiral string forming the driving part (11)of the soft actuator (1) according to an example of the presentinvention. As shown in FIG. 2, the homochiral string is the string inwhich the directions of both twist and coiling are same. The homochiralstring can be contracted as the string is heated by the thermoelectricelement part (13) and can be expanded as the string is cooled by thethermoelectric element part (13).

FIG. 3 illustrates the heterochiral string forming the driving part (11)of the soft actuator (1) according to an example of the presentinvention. As shown in FIG. 3, the heterochiral string is the string inwhich the direction of twist is opposite to the direction of coiling.The heterochiral string can move oppositely to the homochiral string.The heterochiral string can be expanded as the string is heated by thethermoelectric element part (13) and can be contracted as the string iscooled by the thermoelectric element part (13).

In an example of the present invention, the direction of contraction andexpansion of the homochiral or heterochiral string is not limited to thelongitudinal direction of the string. The homochiral string can becalled the first string (1101) or the second string (1103), and theheterochiral string can be called the first string (1101) or the secondstring (1103) that is not the homochiral string. When the first string(1101) and the second string (1103) are arranged one by one withmaintaining some distance between them, it is called the unit body(1100).

FIG. 25 illustrates the unit body (1101) according to an example of thepresent invention.

As shown in FIG. 25, the driving part (11) realizes a single drive ofthe unit body (1100) by cooling one of the strings, the first string(1101) and the second string (1103), and heating the other string by theheat energy delivered from the thermoelectric element part (13).

In an example of the present invention, the unit body (1100) is composedof the first string (1101) and the second string (1103) contracted orexpanded to the opposite direction according to heating or cooling whichare arranged with maintaining some distance. The unit body (1100)composed of those first string (1101) and second string (1103) realizesthe same movement, either contraction or expansion, between the firststring (1101) and the second string (1103) even when they are separatelytreated with heating or cooling, and thereby the unit body (1100)realizes a single driving when current is applied through thethermoelectric element part (13).

FIG. 26 illustrates the driving part (11) or the driving surface (11 aor 11 b) according to an example of the present invention.

In an example of the present invention, the unit body (1100) isconnected to the thermoelectric element part (13) to receive heatenergy. The unit body (1100) can receive different types of heat energyas current flows through the thermoelectric element part (13). Forexample, the first string (1101) can be heated by the thermoelectricelement part (13) and the second string (1103) can be cooled by thethermoelectric element part (13). Or reversely, the first string (1101)can be cooled by the thermoelectric element part (13) and the secondstring (1103) can be heated by the thermoelectric element part (13).Accordingly, those two strings, the first string (1101) and the secondstring (1103) showing different behaviors according to the heat energytype can move to the same direction.

The driving part (11) may have a plurality of the unit bodies (1100)arranged in parallel.

In an example of the present invention, the driving part (11) can havethe structure comprising multiple unit bodies (1100). For example, thedriving part (11) is composed of multiple unit bodies (1100) arranged inparallel.

The first fiber (1101) and the second fiber (1103) of the unit body(1100) forming the driving part (11) can receive different types of heatenergy from the thermoelectric element part (13) to implement the sameoperation. Therefore, in the driving part (11) having various shapes,the conductive body of the thermoelectric element part (13) should beset in a proper arrangement in consideration of the operation direction.The operation direction of the driving part (11) and the setting of thethermoelectric element part (13) are described in more detail in thefollowing example illustrated by FIG. 27.

FIG. 27 illustrates the thermoelectric element part (13) according to anexample of the present invention.

In an example of the present invention, the thermoelectric element part(13) indicates the device using thermoelectric effect.

Thermoelectric effect is the general term for the three heat andelectric correlation phenomena including Seebeck effect, Peltier effect,and Thomson effect. The thermoelectric element part (13) according to anexample of the present invention uses Peltier effect among thosethermoelectric effects.

Peltier effect is understood as the phenomenon that when current isflowing in a metal, heat is flowing together therein and at that timeheat seems to be generated or absorbed on the connection surface due tothe difference in heat flow between two metals. The heat generation andabsorption in Peltier effect is reversible. When one side generates heatby current flow, the other side absorbs the heat. When the direction ofcurrent flow is changed, the heat generation turns to the absorption andthe heat absorption changes into the heat generation. In particular, inPeltier effect, when the current value is increased and the conductormaterial and combination are appropriately selected so that coolingsystem is working by endotherm of the contact point, which is calledthermoelectric cooling. The thermoelectric cooling phenomenon iscurrently used in the temperature range of a freezer, but a method ofmulti-stage cooling to 70K is also being developed.

As shown in FIG. 27, the thermoelectric element part (13) can includethe first conductive body (132), the second conductive body (135)showing different direction of heat flow from the first conductive body(132), and the conductor (133) arranged in series between the firstconductive body (132) and the second conductive body (135).

In an example of the present invention, the thermoelectric element part(13) is composed of the first conductive body (132), the secondconductive body (135), and the conductor (133). In the thermoelectricelement part (13), the first conductive body (132), the secondconductive body (135), and the conductor (133) are arranged in series,so that the current delivered from the power supply part (15) can beconverted into heat energy which is then delivered to the driving part(11). The first conductive body (132) of the thermoelectric element part(13) can be n-type semiconductor or p-type semiconductor, and the secondconductive body (135) of the thermoelectric element part (13) can bedifferent type of semiconductor from the first conductive body (132) inthe thermoelectric element part (13). The conductor, n-typesemiconductor and p-type semiconductor will be described hereinafter.

The conductor (133) is a material having a high electrical conductivityand a high thermal conductivity. That is, it is a material that deliverselectricity and heat well. The conductor (133) refers to thecorresponding term of the insulator. Such metals as gold, silver, andcopper are the typical conductor (133) delivering electricity and heat.Conductors conducting electricity can be classified as solid conductorsand liquid conductors. In particular, the representative solid conductoris metal and the representative liquid conductor is aqueous solution ofacid, alkali, and salt.

In general, when free electrons are plenty in a semiconductor, it iscalled n-type semiconductor. On the contrary, when hole density isbigger than free electron density, it is classified as p-typesemiconductor. The ionized impurity atom that lost electrons is called adonor. When the impurity is the donor, it is n-type semiconductor. Inp-type semiconductor, current is flowing by an acceptor. P-n-ptransistor, n-p-n transistor, or p-n-p-n device can be prepared bycombining the p-type and the n-type semiconductors. The semiconductordiode is the most basic p-n complex.

The thermoelectric element part (13) can heat or cool the conductor(133) by the divided pathways, which are the conduction pathway throughwhich current is delivered to the second conductive body (135) via theconductor (133) after passing through the first conductive body (132);and the other conduction pathway through which current is delivered tothe first conductive body (132) via the conductor (133) after passingthrough the second conductive body (135).

In an example of the present invention, the first conductive body (132),the second conductive body (135), and the conductor (133) are arrangedin series in the thermoelectric element part (13), by which current isprovided from the power supply part (15). The first conductive body(132) or the second conductive body (135) of the thermoelectric elementpart (13) can be connected to the power supply part. The thermoelectricelement part (13) can heat or cool the conductor (133) according to thedirection of current supplied to the first conductive body (132) and thesecond conductive body (135).

The driving part (11) can realize a single drive of the unit body (1100)by shrinking or expanding the first string (1101) and the second string(1103) together as the conductor (133) is heated or cooled.

When current passing through the n-type semiconductor and flowingthrough the conductor (133) to the p-type semiconductor is supplied inthe thermoelectric element part (13), the conductor (133) can be cooled.On the other hand, when current is flowing from the p-type semiconductorand passing through the conductor (133) and then heading to the n-typesemiconductor, the conductor (133) can be heated. The cooled or heatedconductor (133) can deliver heat energy to cool or heat the driving part(11).

In an example of the present invention, the power supply part (15) canform a closed circuit with the thermoelectric element part (13). Thepower supply part (15) can supply current to the thermoelectric elementpart (13). The power supply part (15) selects the direction of currentand transmits energy in the direction of shrinking or expanding thedriving part (11). The power supply part (15) can comprise anyconfiguration that may be installed in the driving part (11), installedin the string part (17, FIG. 28), or installed outside the soft actuator(1) to provide current.

<Example 1> Soft Actuator (1) Comprising the String Part (17)

FIG. 28 illustrates the soft actuator (1) including the string part (17)according to an example of the present invention.

The soft actuator (1) according to an example of the present inventioncan have the string part (17) connected in parallel to the side of thedriving part (11) wherein the unit body (1100) is arranged in parallel.The soft actuator (1) can also have the power supply part (15) attachedto the string part (17). In the soft actuator (1), the thermoelectricelement part (13) and the power supply part (15) can make a closedcircuit. In the soft actuator (1), the thermoelectric element part (13)and the driving part (11) cross each other several times. The softactuator (1) can be set to supply same heat energy to one of the firststring (1101) and the second string (1103). The soft actuator (1) caninclude the unit body (1100) and the driving part (11) driving to thesame direction. In the soft actuator (1), the string part (17) cansupport the driving of the driving part (11). The string part (17) ofthe soft actuator (1) can be made of a flexible material. In FIG. 28, itis shown that some of the conductor (133) are installed outside thestring part (17), however the soft actuator (1) can have the structurewherein the conductor (133) having a wide area and the string part (17)are connected. In the soft actuator (1), the power supply part (15)determines the direction of current flow, so that the direction ofcontraction or expansion of the driving part (11) can be regulated. Thesoft actuator (1) having the single driving part (11) prepared in adetachable form on the body can be used as a muscular strength aid toassist muscular strength.

<Example 2> Cylindrical Soft Actuator (1)

FIG. 29 illustrates the cylindrical band of the soft actuator (1)according to an example of the present invention.

FIG. 30 illustrates the spreaded cylindrical band of the soft actuator(1) according to an example of the present invention.

In the soft actuator, the multiple unit bodies (1100) are arranged inparallel to form the driving surface (11 a or 11 b) and the drivingsurface (11 a or 11 b) makes a pair with the string part (17) composedof the flexible string connected to the side of the unit body (1100) inparallel, and these pairs are arranged by turns to form the cylindricalside wall. In the thermoelectric element part (13), a conduction pathwayis formed on the one driving surface (11 a or 11 b) in which current istransmitted to the second conductive body (135) through the conductor(133) via the first conductive body (132), and another conductionpathway is formed on the other driving surface (11 a or 11 b) in whichcurrent is transmitted to the first conductive body (132) through theconductor (133) via the second conductive body (135). This pair ofdriving surfaces (11 a and 11 b) can generate a bending moment byrealizing different drivings during contraction or expansion when it issupplied with current from the thermoelectric element part (13).

In an example of the present invention, the soft actuator (1) can beprepared in the form of a cylinder including hollows. By comprising thedriving part (11) and the string part (17), the soft actuator (1)exhibits the characteristics of a flexible band. By the parallelconnection of the unit body (1100) in the soft actuator (1), the widthof the driving surface (11 a or 11 b) can be changed. The drivingsurface (11 a or 11 b) of the soft actuator (1) can be divided into thefirst driving surface (11 a) and the second driving surface (11 b) thatcan be contracted or expanded differently when current is supplied fromthe power supply part (15). In the soft actuator (1), the thermoelectricelement part (13) and the power supply part (15) can form a closedcircuit. In the soft actuator (1), the power supply part (15) can beplaced in the string part (17). In the first driving surface (11 a) andthe second driving surface (11 b) of the soft actuator (1), n-typesemiconductor or p-type semiconductor is arranged differently, so thatthe first driving surface (11 a) and the second driving surface (11 b)can be contracted or expanded by the direction of current.

As shown in FIG. 30, the driving surface (11 a or 11 b) is supplied withcurrent in the other direction from the power supply part (15) torealize two kinds of bending moments. The power supply part (15) cansupply current to the right or to the left. Therefore, when current issupplied from the power supply part (15) to the driving surface (11 a or11 b) to the direction of right, the first driving surface (11 a) isexpanded, and therefore the second driving surface (11 b) is contracted.On the other hand, when current is supplied from the power supply part(15) to the driving surface (11 a or 11 b) to the direction of left, thefirst driving surface (11 a) is contracted and therefore the seconddriving surface (11 b) is expanded. The opposite driving between thefirst driving surface (11 a) and the second driving surface (11 b) cangenerate a bending moment in the cylindrical soft actuator (1). Thecylindrical soft actuator (1) that can generate a bending moment can beused as a muscular strength aid to support muscular strength by beingworn on some body parts with joints, such as elbows or knees. Inparticular, the cylindrical soft actuator (1) can assist in fast andrepetitive motion, such as climbing stairs when worn on a user's knee.

Those skilled in the art will appreciate that the conceptions andspecific embodiments disclosed in the foregoing description may bereadily utilized as a basis for modifying or designing other embodimentsfor carrying out the same purposes of the present invention. Thoseskilled in the art will also appreciate that such equivalent embodimentsdo not depart from the spirit and scope of the invention as set forth inthe appended Claims.

FIG. 31 is the perspective view of the soft actuator according to anexample of the present invention.

As shown in FIG. 31, the soft actuator (1) can include the driving part(11) and the driving cable (13).

The soft actuator (1) can include the driving part (11) composed of theunit body (1100) comprising the first string (1101) which is twisted andcoiled and the second string (1103) which is also twisted and coiled andplaced with maintaining some distance from the first string (1101); andthe driving cable (12) in which a hollow is formed and the unit body(1100) is inserted into the hollow.

In an example of the present invention, in the driving part (11) of thesoft actuator (1), the first string (1101) has a smaller coiling radiusthan the second string (1103) and the second string (1103) wraps thefirst string (1101) to form the unit body (1100). In the soft actuator(1), the driving part (11) can be introduced into the driving cable (12)to implement the driving of the soft actuator (1).

FIG. 31 illustrates the twisted string that forms the driving part (11)of the soft actuator (1) according to an example of the presentinvention.

As shown in FIG. 31, the string forming the driving part (11) of thesoft actuator (1) of the invention is primarily twisted. To give thetwisted structure to the string forming the driving part (11) of thesoft actuator (1), one end of the string is fixed and the other end ofthe string is rotated or both ends are rotated. The direction of thetwisting in the string forming the driving part (11) of the softactuator (1) itself does not affect the driving of the soft actuator(1), and instead the relation between the coiling direction and twistdirection which will be described hereinafter can determine thecharacteristics of the string. The diameter and the size of the stringforming the driving part (11) of the soft actuator (1) are not limitedand can be different between the first string (1101) and the secondstring (1103).

In an example of the present invention, the string constituting thedriving part (11) of the soft actuator (1) can be selected from thegroup consisting of such polymers as nylon, shape memory polyurethane,polyethylene, and rubber. By using such polymers as the string formingthe soft actuator (1), the soft actuator (1) can maintain the reversiblestructure wherein the string is untwisted and retwisted even at a hightemperature. The string forming the soft actuator (1) can be changed notonly by heating but also by cooling, so that it can provide a reversiblerotation movement to going back to the initial coiled structure.

FIG. 1 illustrates the coiling structure of the string constructing thedriving part (11) of the soft actuator (1) according to an example ofthe present invention.

As shown in FIG. 1, the string forming the driving part (11) of the softactuator (1) can be twisted first and then the twisted string can becoiled additionally. The direction of coiling of the string forming thedriving part (11) of the soft actuator (1) can be equal to or differentfrom the direction of twist. A method to make the string forming thedriving part (11) of the soft actuator (1) coiled is not limited to aspecific one.

As an example, one side of the string is fixed and the other side of thestring is rotated to make the coiling structure. Or, the string wraps apipe to make the string coiled. When the string is twisted and coiled atthe same time, the driving force of the string induced by heating andcooling becomes strong and the characteristics of the string can bechanged according to the direction of the twist and coiling. The volumeof the string forming the driving part (11) of the soft actuator (1) canbe varied from the twist and coiling.

FIG. 4 illustrates the homochiral string forming the driving part (11)of the soft actuator (1) according to an example of the presentinvention.

The homochiral string is the string in which the directions of bothtwist and coiling are same. The homochiral string can be contracted asthe string is heated and can be expanded as the string is cooled.

FIG. 3 illustrates the heterochiral string forming the driving part (11)of the soft actuator (1) according to an example of the presentinvention.

The heterochiral string is the string in which the direction of twist isopposite to the direction of coiling. The heterochiral string can moveoppositely to the homochiral string. The heterochiral string can beexpanded as the string is heated and can be contracted as the string iscooled.

One of the strings, the first string (1101) and the second string(1103), forming the driving part (11) can be the homochiral stringdisplaying that the directions of twist and coiling are same, and theother string can be the heterochiral string displaying that thedirections of twist and coiling are different.

In an example of the present invention, the driving part (11) iscomposed of the first string (1101) and the second string (1103) havingdifferent structures, so that the driving part can realize the differentdrivings by same heat energy. The first string (1101) can be thehomochiral string. At this time, the second string (1103) is theheterochiral string, so that the first string (1101) and the secondstring (1103) display different structures. It is also possible that thefirst string (1101) is the heterochiral string. At this time, the secondstring (1103) is the homochiral string, so that the first string (1101)and the second string (1103) display different structures.

The driving part (11) includes the thermoelectric element (not shown)generating heat with the current provided. The thermoelectric element(not shown) can deliver heat energy to the first string (1101) and thesecond string (1103).

In an example of the present invention, the driving part (11) caninclude the thermoelectric element (not shown) playing a role inconverting electric energy into heat energy in the course of making thefirst string (1101) and the second string (1103) twisted and coiled. Thethermoelectric element (not shown) can be included in the driving part(11) in the form of electrothermal wire or electrothermal coating. Thethermoelectric element (not shown) can heat the first string (1101) andthe second string (1103). The thermoelectric element (not shown) isconnected to the first string (1101) and the second string (1103)separately, so that it can heat the first string (1101) and the secondstring (1103) separately.

FIG. 32 illustrates the unit body (1100) constructing the driving part(11) of the soft actuator (1) according to an example of the presentinvention.

FIG. 33 is a cross-sectional view of the soft actuator (1) according toan example of the present invention.

The driving part (11) can realize different behaviors, eithercontraction or expansion, between the first string (1101) and the secondstring (1103) forming the unit body (1100) when the first string (1101)and the second string (1103) are heated or cooled.

In an example of the present invention, the first string (1101)constituting the unit body (1100) of the driving part (11) can becontracted when it is heated. At this time, the driving part (11) canrealize different behaviors when the first string (1101) and the secondstring (1103) are provided with the same heat energy since the secondstring (1103) forming the unit body (1100) is expanded by heating.Therefore, the first string (1101) and the second string (1103)constituting the unit body (1100) are not heated or cooledsimultaneously, and instead they are heated or cooled independently toinduce the driving of the soft actuator (1).

The driving part (11) can include several unit bodies (1100).

In an example of the present invention, the driving part (11) caninclude one or more unit bodies (1100). The driving part (11) ispenetrated into the driving cable (12) and several unit bodies (1100)can be arranged apart. As the number of unit bodies (1100) included inthe driving part (11) increases, the driving of the soft actuator (1)can be controlled more accurately. However, the number of unit bodies(1100) in the driving part (11) should not exceed the number of unitbodies that may be contained within the volume of the driving cable(12). Preferably, the driving part (11) includes at least three unitbodies (1100). The unit bodies (1100) are not arranged densely on oneside of the driving cable (12) but uniformly disposed on the frontsurface of the driving cable (12) to realize driving of the softactuator (1).

The driving part (11) makes the movement of the driving cable (12) suchas tension, compression, bending, and rotation possible by theindependent driving of several unit bodies (1100) therein.

The independent driving of those multiple unit bodies (1100) makes thetension, compression, bending, and rotation possible, which areillustrated in the following examples in more detail.

The driving cable (12) may have multiple hollows corresponding to thenumber of the unit bodies (1100).

In an example of the present invention, the driving cable (12) can haveenough space to allow multiple unit bodies (1100) to be intruded. Thedriving cable (12) may have the same number of hollows as the number ofunit bodies (1100) to be intruded. The hollows in the driving cable (12)can be uniformly formed on the entire surface of the driving cable (12)without being densely arranged on one side. The hollow of the drivingcable (12) can penetrate one surface of the driving cable (12) and theother surface thereof. The driving cable (12) can wrap one surface orthe other surface of the unit body, so that the unit body (1100) and thedriving cable (12) are driven in the same track. A side wall can be madeof a flexible material to prevent the resistance generated by thedriving cable (12) in the soft actuator.

Hereinafter, the tension, compression, bending, and rotation of the softactuator (1) are described in the following examples. The soft actuator(1) comprising the 4 unit bodies (1100) is described in each example inadvance to describe the driving. As shown in the cross-sectional view,the unit body (1100) sitting at the direction of 12 o'clock is indicatedas (a), and the unit bodies (1100) arranged regularly from the standardposition (a) at the intervals of 90 degree clock-wise are indicaterespectively as (b), (c), and (d).

<Example 3> Tension and Compression

FIG. 34 illustrates the compression or tension of the soft actuator (1)according to an example of the present invention.

In an example of the present invention, the first strings (1101) of theunit body (1100 a)˜the unit body (1100 d) can be heated simultaneously.By that, the soft actuator (1) can be compressed or expanded. Inparticular, when all the first strings (1101) are composed of homochiralstrings, the soft actuator (1) can be compressed by heating the firststring (1101). At this time, the second strings (1103) have to beheterochiral strings, and the soft actuator (1) can be expanded byheating the second string (1103). On the other hand, when all the firststrings (1101) are heterochiral strings, the soft actuator (1) can beexpanded by heating the first string (1101). And at this time, thesecond strings (1103) are necessarily homochiral strings and the softactuator (1) can be compressed by heating the second string (1103).

The compression or expansion can be accomplished when a pair of the unitbodies (1100) facing each other are compressed or expanded. For example,the first strings (1101) or the second strings (1103) of the unit bodies(1100) (a) and (c) are heated simultaneously, the soft actuator (1) canbe compressed or expanded. Also, when the first strings (1101) or thesecond strings (1103) of the unit bodies (1100) (b) and (d) are heatedsimultaneously, the soft actuator 91) can be compressed or expanded.

<Example 4> Bending

FIG. 35 illustrates the bending of the soft actuator (1) according to anexample of the present invention.

In an example of the present invention, the bending movement of the softactuator (1) can be achieved by contracting or expanding each unit body(1100). When all the first strings (1101) of the unit bodies (1100) arehomochiral strings, the unit body (1100) (a) can be independentlycontracted by heating the first string (1101) of the unit body (1100)(a). At this time, all the second strings (1103) of those unit bodies(1100) are heterochiral strings. The not-heated unit bodies (1100)(b)˜(d) are pulled to the direction of the contracted unit body (1100)(a) and then the soft actuator (1) is bending to the direction of (a).At this time, the unit body (1100) (c) can be further expanded byheating the second string (1103) of the unit body (1100) (c). By that,the degree of bending of the soft actuator (1) can be controlled.

By heating the second string (1103) of the unit body (1100) (c), thesecond string (1103) of the unit body (1100) (c) can be expandedindependently. At this time, the non-heated unit bodies (1100) (a), (b),and (d) are pulled back to the opposite direction of the expanded unitbody (1100) (c) and the soft actuator (1) realizes the bending movementto the direction of (a). By heating the first string (1101) of the unitbody (1100) (a), the unit body (1100) (a) can be contracted. In thisway, the degree of bending of the soft actuator (1) can be controlled.

By heating the second string (1103) of the unit body (1100) (a) toexpand thereof and by expanding the second string (1103) of the unitbody (1100) (c) with supplying a large amount of heat energy, thebending movement of the soft actuator (1) can be accomplished to thedirection of (a) due to the difference in length of the expanded unitbodies (1100). The bending movement can be achieved with reference tothe unit bodies (1100) (b), (c), and (d), and accordingly the bendingmovement is possible in 4 directions of up, down, left, and right.

When all the first strings (1101) are heterochiral strings and at thesame time all the second strings (1103) are homochiral strings, thebending movement can be achieved in all four directions of up, down,left, and right by heating the first strings (1101) or the secondstrings (1103) of the unit bodies (1100) (a)˜(d) according to the methoddescribed above.

In an example of the present invention, the bending movement of the softactuator (1) can be achieved to other directions than the fourdirections above by heating the multiple neighboring unit bodies (1100)to contract or expand them. When all the first strings (1101) arehomochiral strings and at the same time all the second strings (1103)are heterochiral strings, the unit bodies (a) and (b) can be contractedby heating the first strings (1101) of the unit bodies (1100) (a) and(b). At this time, the unit bodies (c) and (d) are pulled to thedirection of (a) and (b), by which the soft actuator (1) realizes theright-upward bending movement. The direction of bending can be preciselycontrolled by regulating the amount of heat energy delivered to the unitbodies (1100) (a) and (b). Additionally, the right-upward bendingmovement of the soft actuator (1) can be increased by heating the secondstrings (1103) of the unit bodies (1100) (c) and (d) to cause themexpanded.

In the meantime, the unit body (1100) (c) and the unit body (1100) (d)can be expanded by heating the second strings (1103) of the unit body(1100) (c) and the unit body (1100) (d). At this time, the unit bodies(1100) (a) and (b) are pulled back toward the direction of (a) and (b),by which the soft actuator (1) can achieve the right-upward bendingmovement. Also, the direction of bending movement can be controlled moreaccurately by regulating the amount of heat energy delivered to each ofthe unit body (1100) (c) and the unit body (1100) (d). Additionally, theright-upward bending movement of the soft actuator (1) can be increasedby heating the first strings (1101) of the unit bodies (1100) (a) and(b) to cause them contracted.

By heating the second strings (1103) of the unit bodies (1100) (a) and(b) to expand thereof and by expanding the second strings (1103) of theunit bodies (1100) (c) and (d) with supplying a large amount of heatenergy, the right-upward bending movement of the soft actuator (1) canbe accomplished due to the difference in length of the expanded unitbodies (1100). The bending movement can be achieved with reference toall the unit bodies (1100), and accordingly the bending movement to alldirections including up-right, down-right, up-left, and down-leftdirections can be accomplished.

When all the first strings (1101) are heterochiral strings and at thesame time all the second strings (1103) are homochiral strings, themulti-directional bending movement can be achieved by heating the firststring (1101) or the second strings (1103) of the unit bodies (a)˜(d)according to the method described above.

<Example 5> Rotation

FIG. 36 illustrates the rotation of the soft actuator (1) according toan example of the present invention.

In an example of the present invention, the rotation movement of thesoft actuator (1) can be achieved when the bending movement describedabove continues. First, the bending is achieved to the direction of theunit body (110) (a), and then the bending continues to the direction ofthe unit bodies (110) (b)˜(d) serially, and then the soft actuator (1)rotates clockwise. To accomplish more accurate rotation, the twoneighboring unit bodies (110) are heated simultaneously and the heatenergy delivered to each unit body (110) is regulated, and then thebending direction can be slowly changed. On the other hand, when thebending continues to the direction of the unit bodies (110) (d)˜(b)serially after the bending has been achieved to the direction of theunit body (110) (a), the soft actuator (1) rotates counter-clockwise.The bending direction can be gradually changed by adjusting the heatenergy delivered to each unit body (110) while simultaneously heatingthe two adjacent unit bodies (110). In addition, the rotation speed ofthe soft actuator (1) can be controlled by changing the time intervalfor heating each unit body (110). And the rotation radius of the softactuator (1) can be regulated by applying a method of controlling thedegree of bending described above.

Those skilled in the art will appreciate that the conceptions andspecific embodiments disclosed in the foregoing description may bereadily utilized as a basis for modifying or designing other embodimentsfor carrying out the same purposes of the present invention. Thoseskilled in the art will also appreciate that such equivalent embodimentsdo not depart from the spirit and scope of the invention as set forth inthe appended Claims.

BRIEF DESCRIPTION OF THE MARK OF DRAWINGS

-   -   1, 100, 200, 300, 400, 500, 600, 1000: soft actuator    -   110, 210, 310, 410, 510, 610, 710, 810, 910, 1010: string    -   111, 211, 311, 411, 511, 1101: first string    -   131. 231. 331. 431. 531, 1103: second string    -   120, 220, 320, 420, 520, 620, 1020:

thermoelectric element

-   -   121, 621, 721 a, 721 b, 821, 921: first electrode    -   122, 622, 722 a, 722 b, 822, 922: P-type thermoelectric material    -   123, 623, 723 a, 723 b, 823, 923: N-type thermoelectric material    -   124, 624, 724 a, 724 b, 824, 924: second electrode    -   230, 830: control part    -   340, 940: adhesive layer    -   750: insulating layer    -   11: driving part    -   11 a: first driving surface    -   11 b: second driving surface    -   1100: unit body    -   131: first conductive body    -   133: conductor    -   135: second conductive body    -   15: power supply part    -   17: string part    -   12: driving cable    -   13: thermoelectric element part

What is claimed is:
 1. A soft actuator comprising a string that iscontracted or expanded by heating or cooling; and a thermoelectricelement to heat or cool the string above which is arranged at least onone side of the string.
 2. The soft actuator according to claim 1,wherein the string is twisted or coiled.
 3. The soft actuator accordingto claim 1, wherein the thermoelectric element is arranged at least on apart of the surface of the string.
 4. The soft actuator according toclaim 3, wherein the soft actuator additionally includes a control partto control the direction of current flowing in the thermoelectricelement.
 5. The soft actuator according to claim 3, wherein the softactuator additionally includes an adhesive layer to connect thethermoelectric element to the surface of the string.
 6. The softactuator according to claim 1, wherein the string includes the firststring and the second string and the thermoelectric element is arrangedbetween the first string and the second string.
 7. The soft actuatoraccording to claim 6, wherein the first string displays forward reactionby the thermoelectric element and the second string displays reversereaction by the thermoelectric element.
 8. The soft actuator accordingto claim 6, wherein the thermoelectric element has flexibility.
 9. Thesoft actuator according to claim 1, wherein the thermoelectric elementis arranged on one end of the string.
 10. The soft actuator according toclaim 9, wherein the thermoelectric element is laminated in multiplelayers.
 11. The soft actuator according to claim 9, wherein the softactuator additionally includes an adhesive layer to alter the directionof current flowing in the thermoelectric element.
 12. A soft actuatorcomprising a driving part which is the unit body composed of the firststring that is contracted or expanded by heating or cooling and thesecond string that shows the opposite movement against the first stringand is arranged with maintaining some distance from the first string;and a thermoelectric element part to heat or cool the driving part;wherein the thermoelectric element part has a conductor region to heator cool the first string and the second string.
 13. The soft actuatoraccording to claim 12, wherein the soft actuator additionally includes astring part composed of flexible fibers connected to the side of theunit body in parallel.
 14. The soft actuator according to claim 12,wherein the thermoelectric element part is crossed over the top side orthe bottom side of the first string and the second string, and the firststring and the second string are arranged facing opposite each otherfrom the thermoelectric element part as a center.
 15. The soft actuatoraccording to claim 12, wherein the driving part cools any one of thefirst string and the second string with the heat energy transferred fromthe thermoelectric element part and heats the other string so that theunit body realizes a single drive.
 16. The soft actuator according toclaim 12, wherein the thermoelectric element part includes the firstconductive body; the second conductive body to change the direction ofheat flow differently from that caused by the first conductive body; andthe conductor arranged in series between the first conductive body andthe second conductive body.
 17. A soft actuator comprising a drivingpart containing the unit body composed of the first string which istwisted and coiled and can be contracted or expanded by heating orcooling and the second string which is twisted and coiled and can becontracted or expanded by heating or cooling and is arranged withmaintaining distance from the first string; and a driving cable having ahollow in which the unit body is intruded.
 18. The soft actuatoraccording to claim 17, wherein one of the strings, the first string andthe second string, is the homochiral string wherein twist and coilingare made in the same direction and the other is the heterochiral stringwherein twist and coiling are made in different direction.
 19. The softactuator according to claim 17, wherein the driving part contains thethermoelectric element generating heat with the applied current and thethermoelectric element delivers heat energy to the first string and thesecond string.
 20. The soft actuator according to claim 17, wherein thedriving part includes a plurality of unit bodies and the driving cableincludes a plurality of hollows corresponding to the number of the unitbodies.